This invention relates to a touch screen panel with integral wiring traces which eliminates the bulky and unreliable prior art external wiring associated with touch screen panels and lowers the cost of manufacturing touch screen panel assemblies.
Touch screen panels generally comprise an insulative (e.g., glass) substrate and a resistive layer disposed on the insulative substrate. A pattern of conductive edge electrodes are then formed on the edges of the resistive layer. The conductive electrodes form orthogonal electric fields in the X and Y directions across the resistive layer. Contact of a finger or stylus on the active area of the panel then causes the generation of a signal that is representative of the X and Y coordinates of the location of the finger or stylus with respect to the substrate. In this way, the associated touch panel circuitry connected to the touch panel by wiring traces can ascertain where the touch occurred on the substrate.
Typically, a computer program generates an option to the user (e.g. xe2x80x9cpress here for xe2x80x98yesxe2x80x99 and press here for xe2x80x98noxe2x80x99xe2x80x9d) on a monitor underneath the touch screen panel and the conductive electrode pattern assists in detecting which option was chosen when the touch screen panel was touched by the user.
The application referred to above relates to an improved edge electrode pattern on the resistive layer of the touch screen panel. The instant application relates to an improvement in the prior art wiring harnesses attached to the touch screen.
There are typically four insulated individual wires, each extending along and around the edges of the touch screen panel to each corner of the touch screen panel where the insulation is removed and the wire is hand soldered to a terminal electrode on the panel at each corner of the panel.
One or more additional layers, usually tape, are often used to secure the wires to the edges of the panel and there may be an insulative layer between the wires and the edge electrodes of the panel to electrically isolate the wires from the edge electrodes.
The problem with such prior art devices are numerous. The solder joints are often not very reliable and create solder bumps on the smooth surface. Moreover, the act of soldering the ends of each wire to the corner electrodes can damage the electrodes or even crack the substrate of the touch panel. Also, this assembly process is labor intensive and hence costly.
To reduce noise, a noise shield may be place under the wires. Adequate noise protection, however, may not always be possible. Also, the assembled touch screen panel does not have a finished appearance. Instead, the taped on wires are bulky and readily noticeable and detract from the appearance of the touch screen panel.
It is therefore an object of this invention to provide a touch screen panel with integral wiring traces.
It is a further object of this invention to provide a touch screen panel with integral wiring traces which is more reliable than prior art touch screen panel assemblies.
It is a further object of this invention to provide a touch screen panel which has a more finished, neat, and low profile appearance.
It is a further object of this invention to provide a method of manufacturing a touch screen panel with integral wiring traces.
It is a further object of this invention to provide such a method of manufacturing a touch screen panel with integral wiring traces which eliminates the possibility of damaging the corner electrodes of the touch screen panel and which eliminates the possibility of damaging the touch screen substrate.
It is a further object of this invention to provide such a method of manufacturing a touch screen panel with integral wiring traces which is less labor intensive and less costly than prior art methods.
It is a further object of this invention to provide a touch screen panel with integral wiring traces and a protective coating over both the wire trace pattern and the edge electrode pattern.
It is a further object of this invention to provide a method of manufacturing such a touch screen panel in which the conductive silver paste of the edge electrode pattern and the wire trace pattern is co-fired with the protective coating thereby resulting in a cost and time savings.
This invention results from the realization that a more reliable, less labor intensive, less costly, and more aesthetically pleasing low profile touch screen panel assembly can be effected by integral wiring traces wherein the prior art individual wires are replaced with a wire trace pattern deposited on the resistive layer of the touch screen panel right on the panel either by printing or by some other method and then electrically isolating the wire trace pattern from the edge electrode pattern by laser etching or some other technique.
This invention features a method of manufacturing a touch panel, the method comprising coating a glass substrate with a resistive layer; applying a pattern of conductive edge electrodes to the resistive layer and applying a conductive wire trace pattern to the resistive layer and electrically isolating the conductive edge electrodes from the conductive wire traces.
The conductive layer is typically a tin antimony oxide composition and the glass substrate may be a soda lime glass composition.
The step of applying the pattern of conductive edge electrodes and the wire trace pattern typically includes screen printing silver/frit paste on the resistive layer in the form of the edge electrode pattern and the wire trace pattern. The step of electrically isolating includes using a laser beam to ablate the resistive material between the edge electrodes and the wire traces. The step of applying a protective insulative border layer usually includes screen printing an insulative composition over the edge electrodes and the wire traces. The insulative composition is preferably a lead borosilicate glass composition.
The panel is subjected to an elevated temperature in a first period of time to burn off any organic material and then a dwell period at the elevated temperature to cure the electrodes and wire trace materials and to fuse the insulative border layer material.
The elevated temperature is typically between 500xc2x0 C.-525xc2x0 C., the first time period is approximately 5 minutes, and the dwell period is approximately 2-3 minutes.
A touch panel in accordance with this invention includes a glass substrate coated with a resistive layer on one surface thereof; a pattern of edge electrodes on the resistive layer; a wire trace pattern on the resistive layer; a trench in the resistive layer between the wire trace pattern and the edge electrode pattern to electrically isolate the wire trace pattern from the edge electrode pattern; and a protective insulative border layer over the edge electrode pattern and the wire traces.
The resistive layer may be a tin antimony oxide composition and the glass substrate may be a soda lime glass composition. The pattern of edge electrodes and the wire trace pattern is preferably made of a silver/frit paste composition. The protective insulative border layer is preferably formed from a lead borosilicate glass composition.